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| Illustration 1 | g06206974 |
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View of the left inner frame brake accumulator location (1) Secondary brake accumulator (2) Rear service brake accumulator (3) Front service brake accumulator | |
Secondary brake accumulator (1), front service brake accumulator (3), and rear service brake accumulator (2) are on the left inner frame under the truck bed. The accumulators are charged by the accumulator charging valve. The accumulators supply pressure oil to engage the front and rear service brakes and to release the parking brakes. The valves in the accumulator charge valve control the amount of pressure in the brake accumulators.
The braking system uses check valves between secondary brake accumulator (1), rear service brake accumulator (2), and front service brake accumulator (3) to maintain charge pressure between each accumulator.
Note: After the ignition key is turned to the OFF position, the pressure in the brake system is fully released in approximately 45 seconds. If the engine is shutdown with the engine shutdown switch that is on the left side stairs, the accumulators will slowly leak down to zero pressure.
Accumulator pressure can be checked using a pressure gauge at the pressure tap on the side of the park brake valve. Each accumulator also has a pressure sensor installed, which can be read using Cat ET or the Advisor monitor display in the cab.